
#include "notification_registrar.h"

#include <algorithm>

#include "base/logging.h"
#include "base/threading/platform_thread.h"

#include "notification_service.h"

namespace
{

    void CheckCalledOnValidThread(base::PlatformThreadId thread_id)
    {
        base::PlatformThreadId current_thread_id = base::PlatformThread::CurrentId();
        CHECK(current_thread_id == thread_id) << "called on invalid thread: "
            << thread_id << " vs. "
            << current_thread_id;
    }

}

struct NotificationRegistrar::Record
{
    bool operator==(const Record& other) const;

    NotificationObserver* observer;
    int type;
    NotificationSource source;
    base::PlatformThreadId thread_id;
};

bool NotificationRegistrar::Record::operator==(const Record& other) const
{
    return observer == other.observer &&
        type == other.type &&
        source == other.source;
    // thread_id is for debugging purpose and thus not compared here.
}

NotificationRegistrar::NotificationRegistrar()
{
    // Force the NotificationService to be constructed (if it isn't already).
    // This ensures the NotificationService will be registered on the
    // AtExitManager before any objects which access it via NotificationRegistrar.
    // This in turn means it will be destroyed after these objects, so they will
    // never try to access the NotificationService after it's been destroyed.
    NotificationService::current();
}

NotificationRegistrar::~NotificationRegistrar()
{
    RemoveAll();
}

void NotificationRegistrar::Add(NotificationObserver* observer,
                                int type,
                                const NotificationSource& source)
{
    DCHECK(!IsRegistered(observer, type, source)) << "Duplicate registration.";

    Record record = { observer, type, source, base::PlatformThread::CurrentId() };
    registered_.push_back(record);

    NotificationService::current()->AddObserver(observer, type, source);
}

void NotificationRegistrar::Remove(NotificationObserver* observer,
                                   int type,
                                   const NotificationSource& source)
{
    if(!IsRegistered(observer, type, source))
    {
        NOTREACHED() << "Trying to remove unregistered observer of type " <<
            type << " from list of size " << registered_.size() << ".";
        return;
    }

    Record record = { observer, type, source };
    RecordVector::iterator found = std::find(
        registered_.begin(), registered_.end(), record);
    CheckCalledOnValidThread(found->thread_id);
    registered_.erase(found);

    // This can be NULL if our owner outlives the NotificationService, e.g. if our
    // owner is a Singleton.
    NotificationService* service = NotificationService::current();
    if(service)
    {
        service->RemoveObserver(observer, type, source);
    }
}

void NotificationRegistrar::RemoveAll()
{
    // Early-exit if no registrations, to avoid calling
    // NotificationService::current.  If we've constructed an object with a
    // NotificationRegistrar member, but haven't actually used the notification
    // service, and we reach prgram exit, then calling current() below could try
    // to initialize the service's lazy TLS pointer during exit, which throws
    // wrenches at things.
    if(registered_.empty())
    {
        return;
    }

    // This can be NULL if our owner outlives the NotificationService, e.g. if our
    // owner is a Singleton.
    NotificationService* service = NotificationService::current();
    if(service)
    {
        for(size_t i=0; i<registered_.size(); i++)
        {
            CheckCalledOnValidThread(registered_[i].thread_id);
            service->RemoveObserver(registered_[i].observer,
                registered_[i].type,
                registered_[i].source);
        }
    }
    registered_.clear();
}

bool NotificationRegistrar::IsEmpty() const
{
    return registered_.empty();
}

bool NotificationRegistrar::IsRegistered(NotificationObserver* observer,
                                         int type,
                                         const NotificationSource& source)
{
    Record record = { observer, type, source };
    return std::find(registered_.begin(), registered_.end(), record) !=
        registered_.end();
}